Why your loaf came out flat

Cut it open. The crumb tells you which of two opposite problems you have.

Flat is the one failure where the same symptom has two causes with opposite fixes. Guess wrong and you make it worse. Nobody tells beginners this, which is why people spend months pushing a variable in the wrong direction.

So: knife, one cut through the middle, look at the holes.

What you're seeing

The loaf spread outward instead of upward. It came out wide and low, maybe 2 inches (5 cm) tall where you expected 4 (10 cm). The score didn't open into an ear, it flattened into the surface. It may have visibly slumped the moment you turned it out of the banneton.

The fork: read the crumb

Between the two? Look at the base. Overproofed loaves have a dense, compressed band along the bottom where the structure collapsed onto itself. Underproofed loaves are tight top to bottom, with a damp, gummy strip at the very base.

The cause: fermentation ran past or short of the window

Both branches are the same mechanism at different points on one curve.

Yeast produces CO₂; the gluten network traps it. That network has a peak strength. Before the peak there isn't enough gas and the gluten hasn't been extended enough, so the dough is stiff and the loaf stays small and tight. After the peak, acid and enzymes have degraded the gluten faster than it can hold gas, the network goes slack, and the structure gives out. In the oven it has no strength left to spring, so it spreads.

Overproofed is the more painful one to look at, because the crumb looks almost like great bread. Big holes, irregular structure. What's missing is height: the gas was there, the walls just couldn't stand up.

Temperature moves you along that curve faster than time does. A dough at 78°F (26°C) ferments roughly twice as fast as the same dough at 68°F (20°C). This is why a recipe's "bulk 4 hours" gives one person a flat loaf and another a brick.

Those windows are for a sourdough at 70–75% hydration with 20% levain. Confirm against the dough: a 50–75% volume increase, a domed and slightly bubbled surface, a jiggle when you shake the container.

The fix: move one direction on the curve

Overproofed. Cut bulk fermentation by about 30%, or ferment cooler. Take the dough's temperature after mixing with an instant-read thermometer rather than guessing at room temperature, and shorten the cold retard if you use one.

Underproofed. Add time, or add warmth. An oven with the light on, or a proofing box at 78°F (26°C), removes the variable entirely. The deeper version of this diagnosis is in why your bread is dense. Flat-and-tight and dense-and-tight are the same failure with the same fix.

Change that one variable and bake again before touching anything else.

The other cause: no shaping tension

If the crumb matches neither column, or the fermentation looked textbook and the loaf still spread, the problem is shaping.

Shaping isn't about making a ball. It's building a taut outer skin under tension, a structural container that resists spreading sideways and directs expansion upward. A properly shaped round feels like a drum head and holds a visibly domed profile on the bench for several minutes without slumping.

1. Preshape, then rest. Gather the dough into a loose round and leave it seam-side down on an unfloured patch of counter for 20 to 30 minutes at 68–75°F (20–24°C). It relaxes and becomes shapeable.
2. Shape on a bare surface. Flour under the dough kills friction, and friction is what generates tension.
3. Drag to tighten. After the final fold, pull the shaped dough toward you across the counter with a bench scraper. Two or three passes tightens the skin.
4. Stop if it tears. A surface that breaks open during shaping means you've gone too far, or the gluten was already degraded.
5. Proof in a banneton or a bowl with a floured towel. An unsupported dough spreads during the final proof no matter how well you shaped it.

Shaping tension is why the same dough bakes flat one week and tall the next with no schedule change.

Dutch oven flat vs. sheet pan flat

Flat in a Dutch oven is a dough problem, full stop. The walls physically prevent spreading and trap steam so the crust stays soft during expansion. If it still came out flat, the dough had nothing left to give. Go back to the crumb table.

Flat on a sheet pan or stone is often just the absence of support. Without walls, a dough at 75%+ hydration spreads while it heats, before the crust sets. That's physics, not a fermentation failure. Baking free-form, drop hydration to 65–68%, shape tighter, and preheat a stone or steel at 500°F (260°C) for 45 minutes so the base sets fast enough to limit the spread.

Add steam either way. Dry oven air sets the crust before the loaf finishes expanding, which caps height regardless of everything else.

Is it saveable?

The loaf in front of you, no. Height is decided by the time it leaves the oven.

It's still good food. An overproofed flat loaf is sour and tender and makes excellent toast, croutons and panzanella. An underproofed one is heavy, but it slices thin and grills well.

The next loaf is fixed by one change, and you already know which one: read the crumb, pick the column, move that variable. That's how you find your kitchen's number.

Something else wrong?

• Your starter bubbles but doesn't rise
• Your dough is so sticky
• Your crumb is gummy
• You got no oven spring
• There's mold on your starter
• There's liquid on your starter
• Your crust is wrong
• Your bread is dense

Or start at the diagnosis index.